fix(orm): honor polymorphic write lifecycle (F07)

[andrewzolotukhin]

Variant updates and deletes bypassed the ordinary lifecycle pipeline, so soft-deletable polymorphic entities were physically removed and hooks/timestamps were skipped. This change makes explicit ofVariant() writes and tracked polymorphic saveChanges() use one atomic pipeline for STI and CTI.

• Honor base-schema soft deletion, retaining CTI child data; add restore() and hardDelete() with typed return values.
• Run base/variant hooks once, map updates to the correct tables/columns, and maintain configured timestamps and exact storage values.
• Capture and lock targets inside the transaction, recheck predicates after lock waits, and use savepoints for caller-owned transactions. Preserve optimistic concurrency and only advance tracked values/snapshots after success.
• Fix extension-managed deletion-column visibility; preserve captured scopes and avoid reapplying them to returning rows. Guard identity changes and writes through projections/loaded relations.

The coordinated v5 major changeset and migration guide explain the deletion change: consumers requiring physical removal must use hardDelete().

Validation: npm run lint, npm run build, npm run test (4,721 tests, no type errors), both website typechecks, and npm run test:queries:integration against PostgreSQL 16 (85 tests, including 26 F07 regressions). Coverage includes STI/CTI lifecycle behavior, tracked inserts/updates/deletes, savepoint/outer rollback, FK and hook failures, scopes/pagination, stale versions, concurrent predicate changes, exact bigint keys, and write-surface type checks.